A complex case of delayed diagnosis of ornithine transcarbamylase deficiency in an adult patient with multiple comorbidities.

We report the case of a medically complex African American adult female with ornithine transcarbamylase (OTC) deficiency diagnosed after lifelong protein aversion and new onset of chronic vomiting and abdominal pain with intermittent lethargy and confusion. Symptomatology was crucial to diagnosis as genetic testing did not identify any pathogenic variants in OTC; however, the patient's diagnosis was delayed despite her having longstanding symptoms of a urea cycle disorder (UCD). Her symptoms improved after treatment with a modified protein-restricted diet, long-term nitrogen-scavenger therapy, and supplemental L-citrulline. Adherence to her UCD management regimen remained a challenge due to her underlying frailty and other medical conditions, which included primary renal impairment (further exasperated by type 2 diabetes mellitus) and decreased left-ventricular function. She passed away 3 years after her OTC deficiency diagnosis due to complications of congestive heart failure. Her OTC deficiency did not have a major impact on her final illness, and appropriate OTC deficiency management was provided until the decision was made to withdraw medical care.